1. Field of the Invention
The present invention relates to a brake apparatus for an elevator hoisting machine for braking a brake disk which is fixed to a rotating shaft, for example, an input shaft, for transmitting the rotational force of a drive motor of the hoisting machine to a driving sheave.
2. Description of the Related Art
FIG. 9 is a partially cutaway front view showing a conventional brake apparatus such as disclosed in Japanese Patent Laid-Open No. 4-313590. FIG. 10 is a plan view of FIG. 9. FIG. 11 is a plan view showing an elevator hoisting machine of an elevator which has the brake apparatus of FIG. 9. FIG. 12 is a side view of FIG. 11. In the figures, a hoisting machine body 1 has a speed-reduction gear unit, an input shaft 1a and an output shaft 1b. A rotating force of a drive motor 11 is transmitted to the input shaft 1a, that is a rotating shaft. A driving sheave 2 is fixed to the output shaft 1b.
A brake disk 3 is fixed to the input shaft 1a. A pair of brake arms 4 located at both sides of the brake disk 3 are attached to a housing 5 of the hoisting machine body 1 rotatably through arm pins 4a. Each brake arm 4 has a brake shoe 6 which are contacted with and separated from the brake disk 3 by rotation of the brake arms 4. The brake arms 4 are biased by springs 7 so that the brake shoes 6 are pressed against the brake disk 3.
A pair of levers 8 are attached to the housing 5 rotatably through lever pins 9. When the levers 8 are rotated, the brake arms 4 rotate against the forces of the springs 7, thereby separating the brake shoes 6 from the brake disk 3. An electromagnetic actuator 10 has a plunger 10a which reciprocates in its axial direction. One end portion of the plunger 10a touches the levers 8.
Further, the other end portion of the plunger 10a touches a switch 12 which detects the motion of the plunger 10a, as shown in FIG. 10.
The operation will now be described. The brake disk 3 is frictionally braked by pressing the brake shoes 6 to both side surfaces of the brake disk 3. The pressing forces of the brake shoes 6 is obtained by magnifying the compressive forces of the springs 7 through the brake arms 4. On the other hand, in the case of releasing a braking force, the brake arms 4 are pushed against the compressive forces of the springs 7 by the levers 8. The pushing forces against the brake arms 4 are obtained by magnifying the projecting force of the electromagnetic actuator 10 through the levers 8.
Further, at the time of releasing the braking force, the motion of the plunger 10a is detected by the switch 12, thereby starting the drive motor 11. Furthermore, at the time of maintenance and inspection, when the end portion of a hand-operated release lever (not shown) constructed separately from the brake apparatus contacts the levers 8 and is moved along the axial direction of the plunger 10a, the braking force will be manually released.
In the conventional brake apparatus constructed as described above, it is necessary to transmit the linear motion of the plunger 10a of the electromagnetic actuator 10 to the rotary motion of the brake arms 4 through the levers 8, thereby increasing the number of parts and cost. Further, since the electromagnetic actuator 10 is disposed on the hoisting machine body 1, the size of the whole hoisting machine is increased, while workability at the time of maintenance and inspection is reduced. Especially, when the plunger 10a is removed during maintenance and inspection, it is necessary to first remove the switch 12. Also, the switch 12 is disposed at a high and deep position, so removing the plunger 10a requires much time and labor.